Effects of the supercritical fluid enhanced with co-solvent on the phenolic and flavonoid contents of Pistacia Terebinthus extracts

The turpentine tree (Pistacia terebinthus L.) contains valuable bioactive compounds such as phenolic acids, flavonoids, and terpenes, attracting scientific interest beyond its culinary and aromatic uses. This study evaluated the effects of supercritical CO₂ (SCCO₂) extraction, with and without ethanol (EtOH) as a co-solvent, on the phenolic, flavonoid, anthocyanin, and antioxidant contents of P. terebinthus extracts. The addition of EtOH significantly reduced total phenolic content (32.10 ± 3.80 mg GA/100 g DM) compared to SCCO₂ alone (43.59 ± 4.60 mg GA/100 g DM; P < 0.043), possibly due to ethanol interference, compound-solvent interactions, or matrix-related factors. Flavonoid contents showed similar trends, with pure SCCO₂ yielding the highest levels. This result may be attributed to the hydrophobic nature and complex polyphenolic structures of the flavonoids in the extracts. Both SCCO₂ and SCCO₂-EtOH methods outperformed ultrasound-assisted (US) extraction in flavonoid yield (P < 0.001). However, US extraction resulted in the highest anthocyanin content (5.01 ± 0.49 mg TAC/100 g DM), likely due to its low-temperature conditions that prevent thermal degradation. Overall, SCCO₂ extraction with EtOH co-solvent appears to be a promising approach for efficiently extracting flavonoids, anthocyanins, and antioxidant compounds from P. terebinthus.